This invention relates to the measurement of the functioning of the heart, and, more particularly, to the analysis of cardiac cycle signals.
The heart is a muscle that operates in response to a variety of electrical signals originating both inside and outside the heart. The electrical signals may be monitored and displayed, producing a continuing series of signals familiar to most persons as an electrocardiogram (ECG). These cardiac cycle signals can, in turn, be used to assess the health of the heart and the presence of some types of heart problems.
The analysis and understanding of the signals produced by the heart, and their relation to the health of the heart, is hampered by several circumstances. The electrical signal contains a great deal of information, since the heart beats about once each second. If each period of one second produced identical electrical signals, the analysis of the cardiac cycles would be straightforward. However, that is not the case, and there is typically quite a bit of variation in the heart electrical signal with time. There may be highly regular signals, occasional but still regular signals, and anomalous, nearly one-of-a-kind signals. The measured electrical signal of the heart is therefore in fact a mixture of signals produced in a variety of ways.
Further, the various types of signals may originate in different parts of the heart. As an example, a highly regular electrical signal may originate in one part of the heart. Some electrical signals may originate elsewhere, and may not interfere with the normal production of the regular signals. However, yet other signals, originating in yet other regions of the heart, may interrupt the normal operation of the heart and lead to dysfunctions such as lethal arrhythmias. The understanding of the functioning of the heart in health and in sickness may lie in determining the temporal and spatial relationships of various electrical signals to each other.
Most studies of the heart and its electrical signals have been performed by electrocardiography. Electrical pickup sensors are attached to the surface of the body. The electrical signals produced during the functioning of the heart are detected and recorded, and are available for more detailed studies at a later time. The electrocardiogram has the disadvantage that it cannot readily determine the precise physical location of the origin of the signals.
There is therefore a need for an improved approach to the study of the heart in which both the time series and physical origin of electrical signals can be measured. It is also necessary to identify the information of value from the mass of electrical signal information, and to use that information in the temporal and spatial analyses. The present invention provides a necessary advance in the art toward fulfilling this need, and further provides related advantages.